電激發量子點光子晶體面射型雷射

Abstract

本論文利用氧化銦錫作為元件的透明導電層，並藉由電流侷限結構控制電流的分布與減緩光子晶體的邊界損耗，成功展示常溫操作的電激發砷化銦量子點光子晶體面射型雷射，其波長在1.3μm附近，最低的閾值電流密度為264.1 A/cm2，由於非完美的光子晶體結構，能帶邊緣模態變為帶狀區域，雷射線寬隨著電流增大而變寬，此外L-I 曲線也有兩段斜率效率，而電流擁擠效應使孔徑邊緣的載子多於中心區域。我們將光子晶體設計於二階Γ點的能帶邊緣，由量測得知Mode B為雷射模態，其近場場形為反對稱的環形電場，且雷射發光面積較大，故遠場場形呈現甜甜圈狀，且沒有特定的極化方向，發散角小於兩度。此外我們藉由變溫量測研究不同週期雷射的溫度相依特性，發現波長失調，與共振腔和增益介質的溫度相依特性會影響雷射對於溫度的敏感度，進而反映在特徵溫度中。另一方面，我們在具有砷化銦量子點與分布式布拉格反射鏡的磊晶結構中製作光子晶體，成功展示光激發具有布拉格反射鏡的光子晶體雷射，為量子點的基態與第一激發態雷射，其中基態雷射的波長約1.3μm，其位於布拉格反射鏡的停止帶內。

In this thesis, electrically pumped InAs quantum-dot photonic-crystal surface-emitting lasers (PCSELs) were successfully demonstrated at room temperature by using Indium-Tin-Oxide (ITO) as transparent and conductive layer, current confined structure to control current distribution and reduce boundary loss of photonic crystal. The lasing wavelengths were around 1.3μm and the lowest threshold current density was 264.1 A/cm2. Because of imperfect photonic crystal, band-edge modes turned into a band and the linewidth became wider while current increased. Besides, there were two parts of slope efficiency. The carrier distribution at the edge of aperture was more than the center because of current crowding effect. We designed photonic crystal at 2nd Γ point and revealed mode B lasing by measurement. Because the near field pattern was anti-symmetric distribution and the emitting area was large, the far field was donut-shape and had no definite polarization. The divergence angle was less than 2 degree. We studied temperature-dependent characteristics of lasers with variable periods by varying measured temperature and found out wavelength detuning, the temperature-dependent properties of cavity and gain media affected the temperature sensitivity of lasers. It reflected in characteristic temperature. On the other hand, we fabricated photonic crystal in the epi-structure with InAs quantum dots and distributed Bragg reflector and successfully demonstrated optically pumped photonic-crystal laser with Bragg reflector. There were ground state and first excited state lasers of quantum dots. The wavelength of ground state laser was around 1.3μm which was in the stop band of Bragg reflector.